Sex-related Differences in Loop Gain during High-Altitude Sleep-disordered Breathing

Area of Science:

• Physiology
• Altitude Medicine
• Sleep Science

Background:

• Central sleep apnea (CSA) is common at high altitudes, particularly in men.
• Increased peripheral chemosensitivity is linked to CSA in men.
• Biological sex may influence acclimatization responses to high altitude.

Purpose of the Study:

• To determine if biological sex affects loop gain (LGn) and CSA severity during acclimatization to 3,800 m.
• To test the hypothesis that CSA worsens with acclimatization in men due to increased LGn, but not in women.

Main Methods:

• Sleep studies were conducted on 20 healthy participants (12 male) at low altitude and during 9-10 days at high altitude.
• CSA severity was measured by the respiratory event index (REI).
• Loop gain (LGn) was quantified using a ventilatory control model.

Main Results:

• CSA severity (REI) was similar between sexes at acute altitude but significantly higher in men at prolonged altitude.
• Men exhibited greater loop gain (LGn) than women at both acute and prolonged high altitude.
• The relationship between REI and LGn was stronger in men, indicating greater instability.

Conclusions:

• Sex-specific differences in loop gain response to high altitude contribute to worsening CSA in men over time.
• Females appear protected from high-altitude-related CSA due to sex-specific acclimatization mechanisms.
• Findings offer crucial sex-specific insights into high-altitude physiology and sleep-disordered breathing.